Paper is a basic material for writing, presswork and printing, and its use has a history over a thousand years. Traditional paper is prepared from plant cellulose and additional auxiliaries by special process. In order to improve paper properties such as whiteness, smooth finish, strength, resolution and the like, a variety of additives such as calcium carbonate, clay, bleaching agent and the like are added as auxiliaries or coatings. Due to development of modern technology and growth of human need, the amount of paper consumed by human beings per year is enormous and increases year by year, leading to increasingly serious problems of disafforestation, environmental pollution, etc. In addition, as lignin in paper yellows under the effect of light and oxygen, paper itself turns yellow along with time, and the quality of writing, presswork and printing is affected badly. Another fatal deficiency of traditional paper is its flammability, which means that books and paper files may burn to nothing in fire. This is one of the main reasons for damage and vanishing of so many paper cultural relics in centuries.
Development of new paper has been started in hopes of solving the environmental problems brought about by traditional paper-making process and improving the utility of the paper. However, it's hard for the utility to achieve the level of traditional paper, and likely pollution to environment occurs in production, application and degradation. In recent years, interest is focused on preparation of paper from inorganic materials as the main components. Nonetheless, such paper preparation is demanding in terms of the inorganic materials which should feature white color, non-toxicity, high flexibility and good processibility into a thin laminate, inter alias. Unfortunately, few inorganic materials can meet these requirements.
As an important calcium phosphate material, hydroxyapatite is the main inorganic ingredient of vertebrate hard tissues, and exhibits the advantages of good biocompatibility, non-toxicity, high whiteness, high temperature resistance, nonflammability, etc. Moreover, hydroxyapatite also exists in sea water in a large quantity. Hence, it owns wide sources and is expected to become an ideal raw material for preparing inorganic paper. However, the use of a hydroxyapatite material is restricted by its poor flexibility. The preparation of a highly flexible hydroxyapatite material is always a big challenge.
Up to now, there is no method in the art for preparing a new hydroxyapatite material having white color, non-toxicity, high temperature resistance, nonflammability, highly flexibility, and good processibility into a thin laminate, which hydroxyapatite material can be used to prepare highly flexible, high temperature resistant and nonflammable hydroxyapatite paper.